Lewis Hamilton's condition is "improving" but Mercedes say they won't know if he will be able to race at F1's season-finale in Abu Dhabi until closer to the weekend, with George Russell - who is taking Hamilton's place for Thursday's media day - ready to jump in the car again if required.
Hamilton, who tested positive for coronavirus on Monday, November 30 and missed last weekend's Sakhir GP, revealed earlier this week that he was back training and was aiming to return this weekend.
But with Hamilton's period of isolation in Bahrain only ending on Thursday, after which he will be allowed to travel to Abu Dhabi if he returns a negative Covid-19 swab, Mercedes, who will do "everything we can" to ensure their star driver's return, admit there are plenty of uncertainties heading to 2020's concluding round.
"There are still some question marks over who will be in the car this weekend in Abu Dhabi," said Mercedes boss Toto Wolff. "Lewis's condition is improving, but we won't know until closer to the time if he will be driving.
"We'll do everything we can to get him in the car and we know he's determined to be back as soon as possible. But his health is our main priority, so we will see what the situation is and then make the call."
Mercedes boss Toto Wolff told Sky F1 after last Sunday's Sakhir GP that Russell, who usually races for Williams and nearly won in Hamilton's place in Bahrain, would again sub for the seven-time world champion if the 35-year-old wasn't able to race.
The earliest Hamilton could possibly fly to Abu Dhabi is Thursday, and practice at the Yas Marina circuit starts on Friday. But Hamilton could conceivably return to action as late as Saturday's qualifying session, as F1 rules state that drivers can compete in the Grand Prix if they have participated in at least one practice session that weekend, of which qualifying is included.
Russell will be answering questions in Mercedes' Abu Dhabi Thursday press conference alongside Valtteri Bottas but will have to wait on Hamilton's condition, and results, to see if he drives the W11 again.
Jack Aitken is similarly in the dark on whether he will continue in Russell's place at Williams.
Speaking in a video posted on his social media on Tuesday from Bahrain, Hamilton said: "Hi everyone. I hope you are all well.
"I know I've not been in touch this past week but it's definitely been one of the hardest weeks that I've had for some time. Just been focusing on recovering and trying to get back in shape so I can get back in the car and race the final race in Abu Dhabi.
"I woke up today feeling great and got my first workout in so I just wanted to send you guys a message of positivity and let you know I'm ok, and thank every single one of you for sending the amazing messages and videos. I really appreciate it."
Hamilton's post did not say he had yet tested negative.
Hamilton has suffered mild Covid-19 symptoms and posted a positive test and retest last Monday. There are extensive protocols being operated around F1's Abu Dhabi race, with a 'biosphere' effectively in place on the Yas Island where the track is. All of the sport's personnel flew to the UAE on Monday from Bahrain.
Reserve driver Stoffel Vandoorne could be an option for Mercedes to participate in Friday practice only if Hamilton was able to return from Saturday onwards.